Lapping tool



Jan. 26, 1943.

D. A. WALLACE LAPPING TOOL Filed .July 1'7, 1940 [N VEN TOR A TT ORN WLL/I directionof thearrows.

' Patented Jan. 26, 1943 David A. Wallace, Detroit, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Application .my 17, 1940, serial No. 346,031

6 Claims.

My present invention is an improvement in mechanism for lapping or surface finishing the interior surfaces of cylindrical bores. The particular improvement has to do with'means for varying the application of pressure upon the surface of the work by the lapping or abrading tools progressively from a higher pressure at the beginning of the iinishing operation toward a lower y pressure at the end of the i-lnishing operation by means automatically releasing the pressure at a predetermined rate. e The principal object of the invention is to provide means whereby cylindrical surfaces may be finished to a greater degree of smoothness by a single tool which commences to operate with a greater degree of pressure upon the surface of the work and progressively operates at lesser pressures upon the surface of the work so as to provide means for smoothing down the abrasions caused by the tool itself as the pressure decreases. A second object of the Ipresent invention is to provide means for automatically timing the duration of the nishing operation, ,the function of the present invention being such asto decrease the pressure of the tool upon the surface of the work toward a final limit at which no work is done upon the interior surface.

These and other objects and advantages of the present invention will be apparent from'the following specication taken in connection with the accompanying drawing which sets forth a preferred embodiment of the invention and wherein like numerals refer to like parts throughout.

In the drawing,

1v disclosesva finishing machine having a :triadev accordancewith the present invenv tion applied thereto;

Fig. 21is an` enlarged vertical section through the tool of thepresentinvention; and,

Fig. 3 is'a horizontal Y.section taken substantially along4 line 3-3 of Fig. 2 looking in the Referring to Fig; 1 there is diseased a finishing machine comprisinga bed plate I0 provided -withrailsfll adaptedrslidably to guide a work.-

supporting Acradley |12 in which is mounted the 'work piecey I3. so as to permit shifting of the work piece to bring'cyli'ndrical bores, suchas-bore IA, therein insverticalalignment with the finishin g tool I5. A standard I6 at the side of the bed ing member by connecting rod 20. Fluid pressure maybe applied below-the piston through pipe.2I in order to raise the supporting member, or above the piston through pipe 22 in order to lower it. Suitable valve means are provided to permit such raising and lowering operations, such valve means not being shownsince they are well understood and from no part of the present invention. The supporting member I1 supports an electric motor 25 which is controlled .bya switch operating lever 26 mounted upon the supporting member and movable therewith to engage a switch lever 21 extending from the control switch 28 -mounted upon standard I6. As the piston I9 raises the supporting memben. lever 26 engages lever 21 to stop the motor.v and then through overriding provisions (not shown) passes above the lever 21. When the pitson I9 lowers the supporting member, lever 26 reengages lever 2l to start the motor. The switching mechanism is not fully illustrated herein since such devices are well known in the art and form'no part of the present invention.

Motor 25 is provided'with an eccentric 30 which drives a connecting member 3|, the lower'end of which is pivotally fastened to a bearing ring 32 j in which is rotatively retained the upper end of simultaneously rotated by motor 36. .The lower end oi' spindle 33 is lconnected to a bifurcated tool carrying member 40, the arms of which are pivotally connected v.to a stirrup. piece 4| having f a cylindrical centrahbo'r'e .in which is bonded a rubber member 42 havlngga smaller cylindrical central bore in which is bonded the hollow upper end of the ,elongated support 43 of the finishing. tool I5.,

is rotated bya worm gear.

The tool I5 comprises the Asup-port 43 in which I' is mounted an axiallymovable'cylinder 44. The

` cylinder 44 is integrally close'd atrits upper end plate I0 is provided with vertical tracks upon which is slidably guided a supporting member Il which maybe moved vertically by the application of fluid pressure to the cylinder I8 in which is mounted a piston I9 connected to the supportand is sealed at its lower end by a plug 45 having a packing gland 46 therein through which extends a piston rod 41 having its vupper end con-4 nected to a piston 43 vertically slidable in the cylinder 44. The piston 4B is provided with a passage 49 in which a removable plug 50 is mounted, the plug being provided with a metering'orice which permits the esca-pe of fluid'from one Side f Piston 48 to the other. side. The plug 50 is screwed into the passage 49 and is provided orifice therethrough to register with the bore The piston 48 is also provided with a large orice 53 extending therethrough in which is mounted a ball check 54 and spring 55 which tends to maintain the ball check in fluid .checking position.

'I'he upper end of cylinder 44 is connected to a plunger 60 which extends through a cap piece 62 threaded onto the upper end of support 43. The plunger 60 is provided with an elongated vertical slot 53 through which passes a crossbar 64 having its ends embedded in the cap piece 62. The lower end of the slot 63 is shaped to provide a lateral extension 65 in which the pin 64 `may be engaged so as to hold the plunger 6U at its uppermost position when the plunger has been manually raised and rotated several degrees through the medium of the knob 6E at its upper extremity. Raising of the plunger 6U and connected cylinder 44 causes relative movement of the cylinder 44 and piston 48 which may be rapidly accomplished since the ball check 54 is raised from its seat so that all of the fluid quickly passes into the space above the piston 4B. At the same time a spring 51 which extends between the cap piece 62 and the top of cylinder 44 is compressed toits greatest extent.

The rod 41 extends through a central bore in the lower end of the support 43 which is so shaped as to provide a support for a, plurality of longitudinallyr extending natural or artificial abrading members. Preferably three such members are provided, of which members 10 and 1| are attached to the surface of the support in fixed relative position and member 12 is mounted in the support in a manner permitting radial movement thereof. The abrading members are preferably equally spaced about the circumference of the lower end of the holding support and are provided with arcuate surfaces to engage the cylindrical bore in which the tool is inserted. Member 12 is mounted upon a. wedge-shaped holding member 13 slidabll7 retained in a vertical slot in the member 43. The lower end of ymember 13 is yieldably retained by a leaf spring 14 fastened to the lower end of support 43 and overlapping the lower end of the member 13. 'I'he upper end of member 13 is similarly yieldably retained as by means of a garter spring 15 encircling the member 43. The rear face of the member 13 is engaged by the outer face of an operating wedge 16 slidably mounted in the support 43 and hav- .ing its upper end attached to the rod 41. The lower end of the operating wedge 16 strikes an adjustable abutment screw 11 extending through the lower end of support 43 and adjustably limiting the downward travel of the operating wedge.

In using the tool the operator pulls upward on knob 66 and rotates it several degrees to engage crossbar 64 in the slot extension 65 in order to hold the plunger 60 inoperative until work is commenced. When the tool is lowered into the bore the knob 6B may be engaged and rotated to release the crossbar 64 from the extension 65, thus permitting the compression spring to move asta-1st cylinder 44. Since this creates a pressure upon piston 48 through the fluid trapped above the piston, pressure will be transmitted through rod 41 to operating wedge 16 to force abrading member 12 outward at a predetermined maximum pressure. The ball check 54 is held against its seat so that only a slight amount of fluid-may escape ythrough the metering device to the lower side of piston 48. As the fluid escapes, the cylinder v44-slides downward in the support 43 permitting will have escaped as entirely to decompress spring 61. By selecting the proper compression spring 61 and by determining the proper rate of escape of the uid through the metering device; the initial force of the Vfinishing tool upon the surface of the work may be set at a predetermined value and the rate of decrease of force and duration of the finishing operation may be fixed at desirable values.

Having described al preferred embodiment of the present invention, it should be apparent to those skilled in the art that the same permits of modification in arrangement and detail. All such modifications as come within the scope of the following claims are considered a part of my invention. Y

I claim:

l. A finishing tool for finishing the surfaces of cylindrical bores comprising an elongated support of lesser Ldiameter than the diameter of the bore to be finishedy and provided with a surface finishing member extending radially beyond the surface of the support, a movable holding member for said finishing member which is slidably guided for radial movement with respect to said support, wedging means slidably guided in said supporting member in wedging contact with said holding member, a piston attached to said wedgng means, a fluid-filled, sealed cylinder in which said piston islocated and which is movably guided in said support and adapted to exert fluid pressure upon said piston when being moved toward said wedging means, and a metering device in said piston for .permitting metered escape of fluid from one side of said piston to the other side when said cylinder is being moved toward said wedging means whereby to release said fluid pressure at a predetermined rate.

2. A finishing tool for finishing the surfaces of cylindrical bores comprising an,elongated support of lesser diameter than the diameter of the bore to be finished and provided with a surface finishing member extending radially beyond the surface cf the suppe-rt, a movable holding member for said finishing member which is slidably guided for radial movement with respect to said support, wedging means slidably guided in said supporting member in wedging contact with said holding member, a piston attached to said wedging means, a fluid-filled, sealed cylinder in which said piston is located and which is movably guided in said support and adapted to exert fluid` pressure upon said piston when being moved to 4 sure exerted upon said piston progressively decreases as said spring decompresses.

3. A finishing tool for finishing the surfaces of cylindrical bores comprising an elongated support of lesser diameter than the diameter of the bore to be finished and provided with a surface finishing member extending radially beyond the surface of the support, a movable holding member for said finishing member which is slidably guided for radial movement with respect to said support, wedging means slidably guided in said supporting member in Wedging contact with said holding member, a piston attached to said wedging means, a fluid-filled, sealed vcylinder in which said piston is located and which is movably guided in said support and adapted to exert fluid pressure upon said piston when being moved toward said wedging means, a metering device in said piston for permitting metered escape of iiuid from one side of said piston to the other side when said cylinder is being moved toward said wedging means whereby to release said fluid pressure at a predetermined rate, a compression' spring adapted to effect movement of said cylinder toward said Wedging means whereby the pressure exerted upon said piston progressively decreases as said spring decompresses, means to move said cylinder"I in the opposite direction to compress said spring, and a check valve in said piston opening on such opposite movement to permit rapid return ofthe iiuid in said cylinder to said one side of the piston.

4. A finishing tool for finishing the surface of cylindrical bores comprising an elongated support of lesser diameter than the diameter of the bore to be finished and provided with a plurality of circumferentially spaced, longitudinally extending surface finishing members extending radially beyond the surface of the support, a movable holding member for at least one of said finishing members which is slidably guided for radial movement with respect to said support, anl

operating wedge slidably guided in said support in Wedging contact with said holding member, a piston attached to said operating wedge, a sealed, movable cylinder in which said piston operates and which is slidably guidedin said support, a spring adapted to be compressed by relative movement of saidmovable cylindextand said support in one diretcion, anda metering device in said piston to permit metered escape of fluid contained in said cylinder from one side of said piston to the other during relative movement of said cylinder and said support in the opposite direction by the decompression of said spring.

5. A finishing tool for finishing the surfaces of. cylindrical bores comprising an elongated support of lesser diameter than the diameter of the -bore to be finished and provided with a plurality of circumferentially spaced, longitudinally ex' tending surface finishing members extending radially beyond the surface of the support, a movable holding member for at least one of said finishing members which is slidab-ly guided for radial movement -with respect to said support, and mechanism for causing such radial movement including a piston and a spring adapted to be compressed to exert a predetermined initial pressure through the medium of said piston to the surface finishing members, said mechanism including means for releasing the compression of said spring an amount in addition to the reduction in i compression thereof resulting from abrading of said bore and at a predetermined rate during operation of said finishing tool whereby the pressure exerted by said surface finishing members progressively decreases as said spring approaches its normal length.

6. A finishing tool for finishing the surfaces of cylindrical bores comprising an elongated support of lesser diameter than the diameter of the bore to be nished and provided with a plurality of circumferentially spaced, longitudinally extending surface iinishing members extending radially beyond the surface of the support, a movable holding member for at least one of said iinishing members which is slidably guided for radial movement with respect to said support, means for causing such radial movement including a piston and a spring adapted to be compressed to exert a predetermined initial pressure through the medium of said piston to the surface iinishing members, a cylinder in which said piston is slidable, and an orifice permitting regular escape of a fiuid from one sideof said piston .to the other in said cylinder under compulsion of the force of said spring whereby the pressure exerted by said surface finishing members progressively decreases as said spring is released from compression. i

DAVID A. WALLACE. 

